Cancer patients unaware of herb/drug interactions
taking herbal remedies and supplements alongside conventional
treatment but this may put them at increased risk of dangerous side
effects, say researchers.
The team, led by Dr Ursula Werneke at Homerton Hospital's psychiatric unit in London, said they issued warnings to 12 per cent of patients studied as their use of garlic, cod liver oil and St John's wort could interfere with some standard cancer treatments.
More than 300 patients attending an outpatient clinic at a specialist cancer centre in London's Royal Marsden Hospital completed multiple-choice questionnaires for the study. They revealed that over 50 per cent of them took supplements - 42 per cent of these were taking only supplements, 10.4 per cent herbals only and the rest were taking a combination of both.
Fewer than half those taking complementary medicine had discussed this with the doctor overseeing their conventional treatment, said the researchers, writing in this week's issue of the British Journal of Cancer.
The report also found that around one third of those patients were unsure of the purpose of the remedy they were taking. And 11 per cent of patients reported taking supplements higher than the recommended doses.
Some complementary medicines are known to react with conventional treatments but recent research has found many consumers to be unaware of the potency of herbals. Garlic and cod liver oil are anticoagulants and may exaggerate the effect of blood thinning drugs taken by some cancer patients while StJohn's Wort can interfere with the action of hormones, antibiotics and chemotherapy.
Researchers were also concerned about echinacea which has effects on the immune system and may compromise some types of cancer treatments for lymphoma and leukemia. Most of their warnings were for use of echinacea in patients with lymphoma. They also warned about use of gingko, kava kava and beta-carotene in smokers.
Dr Werneke said the study highlights the importance for conventional healthcare professionals to discuss complementary medicine with their patients and for doctors to ensure they are properly briefed on how health remedies interact with standard treatment.
"The real problem is that doctors may not have the expertknowledge needed to deal with so many potential risks when patients are mixing conventional treatment with alternative remedies. They need to avoid uncritical encouragement. Also there is not always time to discuss it in routine outpatient clinics."
Echinacea, evening primrose oil, and gingko were among the most common plant-based supplements taken by patients while combinations of vitamins, cod liver oil and selenium were the most popular food supplements.
The researchers did note that they had not identified how the potential risks translate into actual events and research is needed to establish the frequency and seriousness of such side effects.
"Research on CAMs and their interactions with conventional medicines need to keep pace with the development of new cancer therapies," added the authors.
Professor Robert Souhami, director of Clinical and External Affairs at Cancer Research UK said: "This research is very valuable in that it indicates more work needs to be done to get a clearer picture about how complementary medicines react withconventional drugs so patients can receive the best possible advice concerning their treatment."